system("CLS"); cout << "———————————————————————————————————————————————————查询图书信息—————————————————————————————————————————————————————\n" << endl; cout << "按id查找图书信息\n" << endl; cout << "请输入要查询的书籍ID："; cin >> book_id; sql = "select * from books where books_id = " + to_string(book_id); if (mysql_query(&mysql, sql.c_str())) { cout << "Error: Query[查询成功] fail." << endl; break; } res = mysql_store_result(&mysql); //查询结果集 row = mysql_fetch_row(res); cout << "编号: " << row[0] << " 书名: " << row[1] << " 当前数量: " << row[2] << " 价格:￥" << row[3] << " 作者:" << row[4] << " 类型:" << row[5] << endl; cout << "——————————————————————————————————————————————————————————————————————————————————————————————————————————————————\n" << endl;解释一下这段代码

这段代码是一个查询图书信息的功能实现，包括以下步骤：

1. 清空控制台屏幕。

2. 输出查询图书信息的标题。

3. 输出按ID查找图书信息的提示。

4. 让用户输入要查询的书籍ID。

5. 构造SQL查询语句，从数据库中查询对应ID的图书信息。

6. 执行SQL查询语句并检查是否执行成功，若失败则输出错误信息并终止程序。

7. 获取查询结果集。

8. 从结果集中获取一行记录。

9. 输出该书籍的编号、书名、当前数量、价格、作者和类型等信息。

10. 输出查询结果的分割线。

总体来说，这段代码实现了从数据库中查询指定ID的图书信息，并将查询结果输出给用户的功能。

相关问题

c++——文字rpg游戏

以下是一个简单的C++文字RPG游戏的示例代码，其中包括了基本的角色、战斗和物品系统：

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>

using namespace std;

// 角色类
class Character {
public:
    string name;
    int hp;
    int atk;
    int def;
    int gold;

    Character(string n, int h, int a, int d, int g) {
        name = n;
        hp = h;
        atk = a;
        def = d;
        gold = g;
    }

    // 攻击函数
    void attack(Character& other) {
        int damage = atk - other.def;
        if (damage < 0) {
            damage = 0;
        }
        other.hp -= damage;
        cout << name << "攻击了" << other.name << "，造成了" << damage << "点伤害。" << endl;
    }

    // 是否死亡
    bool isDead() {
        return hp <= 0;
    }
};

// 物品类
class Item {
public:
    string name;
    int price;
    int hp;
    int atk;
    int def;

    Item(string n, int p, int h, int a, int d) {
        name = n;
        price = p;
        hp = h;
        atk = a;
        def = d;
    }
};

// 商店类
class Shop {
public:
    Item items[3];

    Shop() {
        items[0] = Item("草药", 10, 20, 0, 0);
        items[1] = Item("铁剑", 50, 0, 10, 0);
        items[2] = Item("铁甲", 100, 0, 0, 10);
    }

    // 显示商店物品
    void showItems() {
        cout << "欢迎光临！以下是本店的物品：" << endl;
        for (int i = 0; i < 3; i++) {
            cout << i + 1 << ". " << items[i].name << " - " << items[i].price << "金币" << endl;
        }
    }

    // 购买物品
    bool buy(Character& c, int choice) {
        if (c.gold < items[choice - 1].price) {
            cout << "金币不足，法购买！" << endl;
            return false;
        }
        c.gold -= items[choice - 1].price;
        c.hp += items[choice - 1].hp;
        c.atk += items[choice - 1].atk;
        c.def += items[choice - 1].def;
        cout << "购买成功！" << endl;
        return true;
    }
};

// 战斗函数
void battle(Character& player, Character& enemy) {
    cout << "你遇到了一只" << enemy.name << "，准备战斗！" << endl;
    while (!player.isDead() && !enemy.isDead()) {
        player.attack(enemy);
        if (enemy.isDead()) {
            cout << enemy.name << "被你打败了！" << endl;
            player.gold += enemy.gold;
            return;
        }
        enemy.attack(player);
        if (player.isDead()) {
            cout << "你被" << enemy.name << "打败了！" << endl;
            return;
        }
    }
}

int main() {
    srand(time(NULL)); // 初始化随机数种子

    // 初始化角色和商店
    Character player("勇者", 100, 10, 5, 50);
    Character enemies[3] = {
        Character("史莱姆", 30, 5, 2, 10),
        Character("骷髅兵", 50, 10, 5, 20),
        Character("巨龙", 100, 20, 10, 50)
    };
    Shop shop;

    // 游戏循环
    while (true) {
        cout << "你的状态 - HP:" << player.hp << " ATK:" << player.atk << " DEF:" << player.def << " 金币:" << player.gold << endl;
        cout << "请选择操作：" << endl;
        cout << "1. 进入商店" << endl;
        cout << "2. 进行战斗" << endl;
        cout << "3. 离开游戏" << endl;
        int choice;
        cin >> choice;
        switch (choice) {
        case 1:
            shop.showItems();
            cout << "请选择要购买的物品（输入编号）：" << endl;
            cin >> choice;
            shop.buy(player, choice);
            break;
        case 2:
            battle(player, enemies[rand() % 3]);
            break;
        case 3:
            cout << "游戏结束，欢迎再次光临！" << endl;
            return 0;
        default:
            cout << "无效的操作！" << endl;
            break;
        }
    }

    return 0;
}

汉诺塔问题——循环算法

汉诺塔问题是一个经典的问题，源于印度一个古老传说。问题是将一根柱子上的64片黄金圆盘按照大小顺序重新摆放到另一根柱子上，且在任何时候，小圆盘上不能放大圆盘，且一次只能移动一个圆盘。

汉诺塔问题的循环算法可以使用迭代的方式来解决。下面是一个示例代码：

#include <iostream>
#include <stack>
#include <string>
using namespace std;

void hanoiTowerIterative(int N, string from, string to, string help) {
    stack<int> s1, s2, s3;
    int moves = (1 << N) - 1;
    for (int i = N; i > 0; i--) {
        s1.push(i);
    }
    if (N % 2 == 0) {
        swap(s2, s3);
    }
    for (int i = 1; i <= moves; i++) {
        if (i % 3 == 1) {
            if (s1.empty() || (!s2.empty() && s2.top() < s1.top())) {
                cout << "Move " << s2.top() << " from " << to << " to " << from << endl;
                s1.push(s2.top());
                s2.pop();
            } else {
                cout << "Move " << s1.top() << " from " << from << " to " << to << endl;
                s2.push(s1.top());
                s1.pop();
            }
        } else if (i % 3 == 2) {
            if (s1.empty() || (!s3.empty() && s3.top() < s1.top())) {
                cout << "Move " << s3.top() << " from " << help << " to " << from << endl;
                s1.push(s3.top());
                s3.pop();
            } else {
                cout << "Move " << s1.top() << " from " << from << " to " << help << endl;
                s3.push(s1.top());
                s1.pop();
            }
        } else {
            if (s2.empty() || (!s3.empty() && s3.top() < s2.top())) {
                cout << "Move " << s3.top() << " from " << help << " to " << to << endl;
                s2.push(s3.top());
                s3.pop();
            } else {
                cout << "Move " << s2.top() << " from " << to << " to " << help << endl;
                s3.push(s2.top());
                s2.pop();
            }
        }
    }
}

int main() {
    hanoiTowerIterative(3, "A", "B", "C");
    return 0;
}